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Comment by nisa | Hacker News Reader

If you reached a point where you need to require bash and not a posix shell and need to enforce these rules just use python or lua if you can or some scheme or whatever else... it's not worth the wasted time hunting bash cruft.

if you are on busybox with ash none of this is helping (except shellcheck which is great).

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Sometimes you just want some 30-50 lines of piping a few commands and a couple of conditionals.

Python (the language with the most community traction to replace bash for scripts) is a royal pain to use for this without libraries that are present in no default system, and even with those it often ends up being more verbose than it should.

> Sometimes you just want some 30-50 lines of piping a few commands and a couple of conditionals.

maybe I was not clear - nothing against shell-scripting but doing some weird dancing like in the article is imho useless, also depending on bash is a stupid idea imho.

posix sh + shellcheck is all you need. if you can't solve your problem in posix sh rethink your code / approach and simplify until it will work.

I agree.

I've used this page successfully as reference for portable syntax:

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3...

Some sections on features I use heavily:

- Parameter Expansion (specifically :-, %, %%, #, ##)

- Special Parameters (specifically "$@", $#, $?)

- set --, this lets you set the $1, $2, etc. variables. I use this with "$@" for arrays, primarily for building command strings.

Here's an small shell script demonstrating some of them:

    #!/bin/sh
    
    # err function
    err() { echo "$1" >&2; exit 1; }
    
    # init variables
    unset src
    unset dst
    dry_run=false
    
    # get arguments
    while [ $# -gt 0 ]; do
        case "$1" in
            -d|--dry-run) dry_run=true ;;
            --) shift; break ;;
            -*) err "unknown option: $1" ;;
            *)
                if [ -z "$src" ]; then src="$1"
                elif [ -z "$dst" ]; then dst="$1"
                else err "unexpected argument: $1"
                fi
            ;;
        esac
        shift
    done
    
    # sanity checks
    ## TODO: print usage
    if [ -z "$src" ]; then err "source not specified"; fi
    if [ ! -d "$src" ]; then err "source does not exist"; fi
    if [ ! -r "$src" ]; then err "cannot read source directory"; fi
    
    if [ -z "$dst" ]; then err "destination not specified"; fi
    
    if ! rsync --version >/dev/null 2>&1; then
        err "missing rsync(1)"
    fi
    
    # build rsync command
    set -- rsync -aq "$src" "$dst"
    
    # log command
    echo "copying $src to $dst"
    echo "    $@"
    if ! $dry_run; then
        if "$@"; then
            echo "success"
        else
            # rsync will have printed an error message
            err "rsync exited with error code $?"
        fi
    else
        echo "dry run; not executing"
    fi

Also be sure to read the man page for test (the [ command).

For typical system scripts, ansible is much better than bash. It has all the commands that are missing from Unix and it's not subject to the bash problems mentioned here.

I agree that python is a pain. It's too low level for any task.

I still use bash a lot though, it's just handy, with lua and python you will have to deal with various of its packages sooner or later, for bash it is just one binary and you get 90% scripting tasks covered, zero dependencies.

if you need arrays use mksh - https://www.mirbsd.org/mksh.htm - if you need complex scripting with small footprint and standard compliance avoid bash and use mksh.

You can count on bash being present on almost any Linux system, other than tiny embedded ones. You can't count on mksh being anywhere unless you install it.

Doesn't matter if it's better or worse, it isn't omnipresent.

actually I do lots of embedded, busybox is about 2MB and bash is 1MB, unless the resource is extremely restricted I just install bash for scripting purposes.

python is about 4.5MB and Lua is about 200K, both run on top of a shell anyways, and need some packages to be fully useful.

To be fair adding 200KB Lua (no luarocks etc) on top of a shell is useful sometimes on embedded system, but I rarely need that.

In addition to bash itself being widespread, most of the common "bashisms" are also supported by zsh and most variants of ksh (and many systems actually use some variant of ksh disguised as /bin/sh). This is unsurprising given that bash itself was originally meant to be a clone of ksh. The places where they differ tend to cluster around uncommon/newer features (like coprocesses), certain syntactic quirks (but if you're aware of them they're usually easy to work around), and interactive features (which are mostly irrelevant for scripts). If you're writing simple scripts (or you're writing complex ones in a careful way), you can reasonably "target" bash and expect them to work on other common shells.

If you're going to be distributing shell scripts, it's probably a good idea to test them on a handful of common shells anyway. If portability between shells isn't something you're worried about, it's exactly as reasonable to ask users to install bash as it is to ask them to install mksh or zsh (or even python or lua or whatever) anyway. If you're most comfortable with bash, just use bash!

But for the love of god and all that is holy, please don't write csh scripts ;)

Bash is available on almost every system. The portability is desirable sometimes.

How many people need that portability? Most of the shell scripts are quick work that needs to run on small amount of environments.

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